video: fbdev: arcfb: add missed free_irq and fix the order of request_irq

The driver forgets to free irq in remove which is requested in
probe.
Add the missed call to fix it.
Also, the position of request_irq() in probe should be put before
register_framebuffer().

Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200324132353.21785-1-hslester96@gmail.com